Fluidic adaptive spark advance system

ABSTRACT

SPARK TIMING IN A SPARK IGNITION ENGINE IS CONTROLLED TO PROVIDE MAXIMUM ENGINE TORQUE BY UTILIZING A FLUIDIC LOGIC CIRCUIT IN COMBINATION WITH AN ACTUATOR FOR SELECTIVELY ADVANCING AND RETARDING SPARK TIMING IN RESPONSE TO FLUID SIGNALS AND A SENSOR FOR DETECTING INCREASING AND DECREASING ENGINE TORQUE. AT ANY GIVEN ENGINE SPEED THE LOGIC CIRCUIT SEEKS THE ACTUATOR DIRECTION WHICH PRODUCES INCREASING TORQUE BY PROVIDING SIGNALS WHICH MOVE THE ACTUATOR ALTERNATELY TO ADVANCE AND RETARD THE SPARK TIMING AND BY SENSING THE RESULTING INCREASE OR DECREASE IN ENGINE TORQUE. AN INCREASE IN ENGINE TORQUE CAUSES THE CIRCUIT TO CONTINUE TO MOVE THE SPARKTIMING ACTUATOR IN THE SAME DIRECTION, A DECREASE IN ENGINE TORQUE RESULTS IN A REVERSAL OF THE ACTUATOR DIRECTION. THE SPARK TIMING IS THEREFORE ADJUSTED UNTIL THE MAXIMUM TORQUE IS REALIZED AND THE CONTROL SYSTEM THEN ENTERS A LOW-AMPLITUDE MODE OF OSCILLATION ABOUT THE MAXIMUM-TORQUEPRODUCING ACTUATOR POSITION UNTIL A TORQUE VARIATION IS ONCE AGAIN SENSED.

United States Patent [72] Inventor Romald E, Bowles Silver Spring, Md. [21] Appl. No. 738,575 [22] Filed June 20, 1968 [45] Patented June 28, 1971 [731 Assignee Bowles Fluldim Corporation Silver Spring, Md.

[54] FLUIDIC ADAPTIVE SPARK ADVANCE SYSTEM 16 Claims, 3 Drawing Figs.

[52] 0.8. CI 180/64, 123/117, 137/12, 137/81.5 [51] Int. Cl B601: 27/06 50] Field oiSearch 180/54, 64, 66; 123/117; 137/81.5,2, 12

[56] References Cited UNITED STATES PATENTS 962,131 6/1910 Dayes 123/1l7X 1,905,941 4/1933 Lansing... 180/54 1,908,551 5/1933 Mallory 123/117(.1) 2,167,902 8/1939 Nallinger 123/117 2,427,407 9/1947 Hill 123/1 l7(.1) 3,037,574 6/1962 Clerk. 180/54UX TORQUE \NCRERSING SIGNRL 3,272,191 9/1966 Walker 3,395,718 8/1968 Wolff ABSTRACT: Spark timing in a spark ignition engine is controlled to provide maximum engine torque by utilizing a fluidic logic circuit in combination with an actuator for selectively advancing and retarding spark timing in response to fluid signals and a sensor for detecting increasing and decreasing engine torque. At any given engine speed the logic circuit seeks the actuator direction which produces increasing torque by providing signals which move the actuator alternately to advance and retard the spark timing and by sensing the resulting increase or decrease in engine torque. An increase in engine torque causes the circuit to continue to move the sparktiming actuator in the same direction; a decrease in engine torque results in a reversal of the actuator direction. The spark timing is therefore adjusted until the maximum torque is realized and the control system then enters a low-amplitude mode of oscillation about the maximum-torque-producing actuator position until a torque variation is once again sensed.

TORQUE DECREQSlNG PU LSE FLUIDIC ADAPTIVE SPARK ADVANCE SYSTEM BACKGROUND OF THE INVENTION The present invention relates to adaptive fluidic control systems, and more particularly a fluidic system for controlling engine spark timing to provide maximum engine torque.

Most automotive spark ignition engines are equipped with two types of spark advance systems. The first, a vacuum advance, compensates for variations in the burning rate of different fuel-air mixtures whereby the ignition spark is produced at an earlier time in the engines cycle for lean mixtures than for faster burning mixtures. Vacuum advance is generally accomplished by a diaphragm-spring assembly attached to the breaker point plate of the distributor, the diaphragm being actuated by pressure in the engine manifold. In the second type of system, compensation is provided for increasing engine speed. Typically, in such a system, a weight is attached to the breaker cam at the distributor, the weight being acted upon by variation in centrifugal force to advance or retard the spark timing by changing the angular position of the breaker cam relative to the drive shaft. Since optimum spark timing depends on a complex combination of factors, including throttle position, engine speed, mixture ratio, compression ratio, and type of fuel, the above described automatic spark advance devices provide only a partial accommodation for varying en gine parameters.

FIG. 1 is a plot of engine torque variation as a function of spark position in the engine cycle at a given engine speed. For each engine speed the general shape of the curve is the same, but the peak or maximum torque point on the curve changes position with changing speed. Prior art automatic spark advance systems cannot fully accommodate the shift of the maximum torque point, and consequently, the spark timing does not maximize torque at all engine speeds. This is further illustrated in FIG. 2 where a number of spark position curves such as that illustrated in FIG. 1 are superimposed on a typical torque versus engine speed plot shown as a solid line. The torque versus engine speed plot of FIG. 2 represents a typical engine operating with the benefit of prior art spark advance controls such as those types described above. The torque is shown to vary sharply depending upon the amount by which spark timing varies from the optimum setting at a particular engine speed. Ifa spark advance system were available to adjust spark timing for maximum torque at any engine speed, the torque developed by the engine would be substantially higher throughout the entire engine speed range, as shown by the dashed line in FIG. 2.

It is an object of the present invention to provide a fluidic spark advance system which changes spark-timing position so as to maximize engine torque and thereby enable an engine to operate at maximum torque for all engine speeds.

In addition, it is an object of the present invention to provide a fluidic adaptive control circuit having general applicability and by means of which a system parameter can be maximized in response to sensed parameter variations.

SUMMARY OF THE INVENTION In accordance with the principles of the present invention a fluidic logic circuit and two fluid-mechanical interfaces are provided to control spark timing in order to achieve maximum torque for all operating speeds of a spark ignition engine. A fluidic oscillator provides a train of fluid pulses as an input signal to a fluidic pulse converter element which alternately switches between two stable states in response to successive input pulses. The pulse converter in turn provides input pulses alternately to one or the other of two control nozzles of a fluidic binary element which has a first stable state in which it displaces a piston actuator in one direction and a second stable state in which it displaces a piston actuator in the opposite direction. Displacement of the piston actuator in one or the other of said directions serves to advance or retard spark timing in the engine. Thus, in the absence of any other input, the alternating output signals from the binary element result in an oscillatory spark advance-retard action. When an increase in engine torque is sensed a fluid signal is applied to a fluidic gate which inhibits application of the train of fluid pulses to the pulse converter and consequently the fluidic binary element is maintained in the one of its stable states in which spark timing is varied to increase engine torque. When a decreasing torque is sensed a pulse is applied to the pulse converter whereupon the fluidic binary element changes state so as to seek a maximum torque. If neither an increasing nor a decreasing torque is sensed, the system returns to an oscillatory mode of operation with the actuator oscillating about the maximum torqueproducing spark-timing position.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plot of engine torque versus spark-timing position for a given engine speed;

FIG. 2 is a plot of engine torque versus engine speed; illustrating both the ideal curve and the curve achievable by prior art spark advance techniques; and

FIG. 3 is a schematic illustration of a fluidic spark advance system in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to FIG. 3 of the accompanying drawings there is illustrated in schematic form a fluidic spark advance system employing the principles of the present invention. A fluidic oscillator 11, having for example the general configuration illustrated in U.S. Pat. No. 3,185,166, provides a continuous train of low frequency output pulses at output passage 13. A source of pressurized fluid P+ is applied to the power nozzle 15 of oscillator 11 to produce a power stream of fluid from power nozzle 15, which due to the configuration of oscillator 11, is normally directed to an output passage 17 of the oscillator 11. Fluid received by output passage 17 is fed back to a control nozzle 19 to deflect the power stream towards output passage 13. When all of the power stream fluid received by output passage 17 prior to deflection of the power stream completes its traversal of the feedback path to control nozzle 19, the control stream issuing from nozzle 19 disappears and the power stream returns to output passage 17. The oscillatory cycle begins again thereby producing the train of pulses at output passage 13. Output passage 13 of oscillator 11 is connected to the input nozzle 23 of a fluidic transmission gate 21. Transmission gate 21 may be of the same general type illustrated in FIG. 4 of U.S. Pat. No. 3,286,086. Pressurized fluid applied to input nozzle 23 of gate 21 normally issues from output passage 25 thereof unless deflected to output passage 27 by a control stream issuing from control nozzle 29. Consequently the train of pulses produced at output passage 13 of oscillator 11 is transmitted through transmission gate 21 via output passage 25 unless pressurized fluid is applied to control nozzle 29.

Output passage 25 of transmission gate 21 is connected to input passage 33 of fluidic pulse converter 31, which for example may be of the type illustrated in U.S. Pat. No. 3,001,698. Pulse converter 31 has two stable states in which it provides a fluid pressure at either of two respective fluid output passages 35 and 37. The state of converter 31, and hence the application of pressurized fluid to output passages 35 and 37, alternates in response to application of successive fluid pulses at input nozzle 33. Output passages 35 and 37 of pulse converter 31 are connected to control nozzles 43 and 45 respectively of fluidic bistable element 41. Bistable element 41, by way of example, may be of the type illustrated in U.S. Pat. No. 3,225,780. A source of pressurized fluid P+ applied to power nozzle 47 of element 41 produces a power stream of fluid which is stable only when directed toward either of output passages 48 and 49 of element 41. The power stream is directed toward output passage 48 in response to application of pressurized fluid at control nozzle 43; the power stream is directed toward output passage 49 in response to application of control fluid at control nozzle 45. In effect then the bistable element 41 provides pressurized fluid signals at output passages 48 and 49 which are amplified versions of the fluid pressure signals appearing at. output passages 35 and 37 respectively of pulse converter 31.

Output passages 48 and 49 of bistable element 41 are connected to provide their fluid pressure signals to a piston chamber 51 on opposite sides ofa piston 53. An actuator 55 is connected to the piston 53 and translatable therewith to advance or retard the timing of the ignition spark at the distributor (not illustrated) in a manner which is conventional in the prior art. The direction of translation of piston 53 determines whether the spark timing is to be advanced or retarded, and the direction of translation of piston 53 is itself determined by the pressure differential produced thereacross by bistable element 41.

The engine frame 61, which is spring mounted at 63 to the chassis of the automobile or other environment in which it operates, is utilized to sense increases and decreases in engine torque. For example, increasing torque causes engine frame 61 to rotate counterclockwise (as viewed in FIG. 3) relative to the chassis whereas decreasing torque causes clockwise (as viewed in FIG. 3) rotation of the engine on its mounts relative to the chassis. Rotation of the engine frame 61 is coupled via coupling members 65 and 67 to translate a diaphragm 69 enclosed within a diaphragm housing 71. A pair of fluid passages 73 and 75 communicate with the interior of diaphragm housing 71 at opposite sides of diaphragm 69. Translation of diaphragm 69 within housing 71 produces a pressure dif ferential across fluid passages 73 and 75, such pressure dif ferential having a polarity which is dependent upon the direction (that is, increasing or decreasing) of engine torque variations. More specifically, for increasing engine torque, the engine rotates counterclockwise as viewed in FIG. 3 and diaphragm 69 moves upward in chamber 71. Consequently an increasing pressure appears at fluid passage 73 and a decreasing pressure appears at passage 75. Similarly, for decreasing torque the diaphragm 69 moves downwardly as viewed in FIG. 3 producing an increasing pressure at fluid passage 75 and a decreasing pressure at passage 73.

Fluid passages 73 and 75 are connected to respective opposed control nozzles 83 and 85 of proportional fluidic amplifier 81. Amplifier 81, by way ofexample, may be ofthe type illustrated in US. Pat. No. 3,275,013. A power stream of fluid is provided by a source of pressurized fluid which is connected to power nozzle 87 of amplifier 81. The power stream is deflected accordingly by the variable differential pressure applied across control nozzles 83 and 85 to produce an amplified version of said variable differential pressure across respective output passages 88 and 89 of amplifier 81. Output passage 88 of amplifier 81, which provides an increasing output pressure signal in response to increasing engine torque, is connected to control nozzle 29 of transmission gate 21. Output passage 89 of amplifier 81, which provides an increasing output pressure signal in response to decreasing engine torque, is connected to input nozzle 93 ofa fluidic pulse generator 9]. Pulse generator 91, by way ofexample, may be ofthe type illustrated in FIG. 2 of US. Pat. No. 3,266,510. Output passage 89 of amplifier 81 is also connected to a control nozzle 95 of pulse generator 91 via a delay path 94. Delay path 94 acts to delay application of pressurized fluid to control nozzle 95 until some predetermined period of time, determined by length of path 94, after application of fluid from passage 89 to input nozzle 93. Upon application of pressurized fluid to input nozzle 93, a power stream is generated which issues from output passage 97. After the predetermined time delay period a control stream is generated from control nozzle 95 in response to reception of pressurized fluid from delay path 94, the control stream acting to deflect the power stream toward output passage 99. Output passage 97 of pulse generator 91 is connected to input passage 33 of pulse converter 31.

ln operation, oscillator 11, operating at a low frequency as determined by the transmission time for fluid between output passage 17 and control nozzle 19, provides a train of fluid pulses for operating the spark advance system in what may be termed the seek mode of the system. Assuming no changing torque sensed at amplifier 81,'the pulse train passes through transmission gate 21 to pulse converter 31. 1f the state to which pulse converter 31, and hence binary element 41, is switched in response to the first control pulse is such that the change in spark timing produces a decrease in engine torque, the decreasing torque will be reflected by a downward movement of diaphragm 69 in chamber 71 whereas to produce an output signal at output passage 89 of amplifier 81. This output signal is converted to a pulse by pulse generator 91 and this pulse is applied to pulse converter 31 causing binary element 41 to reverse its outputs thus reversing the direction of travel of piston 53. This should cause an increasing torque signal to be generated inhibiting the passage of the next pulse through transmission gate 21. In the event that torque does not increase due to malfunction, such as generation of a noise torque decrease signal which passes pulse generator 91 as a double signal such that piston 53 is traveling in an incorrect direction, then no torque-increasing signal is generated and transmission gate 21 passes the next oscillator pulse. Upon application of this pulse to converter 31, the direction of piston 53 is reversed whereby to produce a timing change which causes an increase in engine torque. This increase in engine torque results in an upward movement of diaphragm 69 so as to produce an output signal at output passage 88 of amplifier 81 to inhibit the passage of pulses through transmission gate 21. The state of the pulse converter 31 and hence the state of binary element 41 remains unchanged as long as an increasing torque is sensed at amplifier 81 and therefore the piston 53 continues to be translated to adjust the timing to continue increasing engine torque. This variation in spark timing of course may either be a retardation or advancement depending upon which side of the peak torque point of FIG. 1 the system initially begins operation. Translation of piston 53, and hence advancement or retardation of the spark timing, continues until the spark-timing position passes the point at which there is no further generation of an increasing torque signal and the system enters a seek mode. In the event of an overshoot of the system such that a decreasing torque results, the decreasing torque is sensed by clockwise rotation of the engine frame (as viewed in FIG. 3) relative to the chassis and produces an increasing pressure at output passage 89 of amplifier 81. The signal appearing at output passage 89 initiates a pulse from pulse generator 91, thereby changing the state of pulse converter 31 as well as the state of binary element 41 to reverse the direction of translation of piston 53 of chamber 51. The timing position for the spark is thus varied in the opposite direction, thereby reversing the direction of motion of the operating point on the torque versus spark position curve of FIG. 1 and causing a signal to be generated from output passage 88 during the period ofincreasing torque.

When the spark position is adjusted such that torque is no longer increasing the signal from output passage 88 of amplifier 81 ceases. The removal of the output signal from output passage 88 of amplifier 81 enables transmission of the pulse train from oscillator 11 through gate 21 to pulse converter 31, thereby restoring the seek" mode of operation for the system. In this mode, the system operates in a low amplitude oscillatory cycle about the optimal spark-timing position (i.e. the spark timing which produces maximum engine torque) and at a frequency equal to half that of oscillator 1 1.

It will be apparent that certain modifications can be made to the system illustrated in FIG. 3 without departing from the scope of the present invention. For example, the particular torque sensor, namely spring mounted engine frame 61 and the associated diaphragm follower 69, may be replaced by any conventional torque variation sensing device wherein a fluid pressure is developed as a function of variations in engine torque. Similarly, if a differential pressure is produced at passages 73 and 75 of sufficient magnitude to operate gate 21 and pulse generator 91, amplification by means of proportional amplifier 81 may prove unnecessary and amplifier 81 can be eliminated. Similarly, binary element 41 may be eliminated if the pressure signals appearing at output passages 35 and 37 of pulse converter element 31 are sufficiently large to produce the requisite displacement of the piston 53 in chamber 51.

Similarly the spark-timing advance-retard actuator illustrated schematically as piston 53 in chamber 51 with a follow ing shaft 55 may be any element for converting the differential pressure appearing at output passages 48 and 49 of binary ele ment 41 into a mechanical motion that actuates a conventional spark advance-retard mechanism.

By a simple modification, the system of FIG. 3 may be enhanced to compensate for changes of torque resulting from changed engine throttle settings. For example, depending on the position of piston 53 and actuator 55 when the throttle setting is changed, a fluid signal may be generated as a function of the throttle-setting change and employed in the fiuidic circuit as an input signal. If, for example, engine efficiency is maximized by retarding the spark during deceleration, an appropriate pressure signal could be applied to the piston chamber 51 during deceleration so as to optimize timing for the particular throtte-setting change. Alternately, a signal from the throttle might be applied to amplifier 81 or gate 21 to suppress the effect of the commanded torque change signal received from diaphragm chamber 71 and thereby hold the fiuidic system in the seek mode during throttle changes.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variation of the details of construction which are specifically illustrated and described may be resorted to without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A fluidic adaptive spark-advance system for maximizing the torque developed by a spark ignition engine, said system comprising:

sensing means for sensing variations in the torque developed by said engine;

means for providing differential fluid pressure which varies in a first sense in response to increasing torque and in a second sense in response to decreasing torque;

fluidic oscillator means for providing a continuous train of fluid pulses;

fiuidic pulse converter means responsive to application of successive fluid pulses thereto for alternating between first and second stable states;

fiuidic gating means for normally applying said train of fluid pulses to said fluidic pulse converter means and responsive to said differential fluid pressure varying in said first sense for inhibiting application of said train offluid pulses to said fluid pulse converter means;

fluid pulse generator means responsive to said differential fluid pressure varying in said second sense for applying a fluid pulse to said fluid pulse converter means; and

means responsive to said pulse converter means in said first stable state for advancing spark timing in said engine and responsive to said pulse converter means in said second stable state for retarding spark timing in said engine.

2. The system according to claim 1 further comprising fluidic amplifier means responsive to variations of said differential fluid pressure in said first sense for providing a first actuating fluid signal and responsive to variations of said dif ferential fluid pressure in said second sense for providing a second actuating fluid signal, wherein said fluidic gating means inhibits said train of pulses in response to said first actuating fluid signal and wherein said fluidic pulse generator applies said fluid pulse to said pulse converter in response to said second actuating fluid signal.

3. The system according to claim 2 wherein said sensing means comprises:

means for spring mounting the frame of said engine to a chassis such that for increasing engine torque the engine frame is displaced in a first direction relative to said chassis and for decreasing engine torque said engine frame is displaced in a second direction relative to said chassis;

an enclosed chamber having a translatable diaphragm disposed therein to form two substantially pressure-isolated subchambers within said chamber and having a pair of outlet ports for providing said differential fluid pressure and communicating with respective ones of said subchambers; and

means responsive to displacement of said engine frame in said first and second directions for translating said diaphragm within said chamber in first and second directions, respectively, to thereby vary the pressures in said chambers differentially.

4. A control system comprising:

control means responsive to application thereto of a first control signal for effecting variation of a first system parameter in a first sense, and responsive to application thereto of a second control signal for effecting variation ofsaid first parameter in a second sense;

sensing means for monitoring a variable second system parameter to provide an input signal when said second parameter is varying toward a predetermined value of said second parameter;

means for varying said second system parameter over a range of values including said predetermined value as a function of said first parameter;

means responsive to the absence of said input signal for alternately applying said first and second control signals to said control means; and

means responsive to the presence of said input signal for steadily applying either of said first and second control signals to said control means.

5. The system according to claim 4 wherein said second parameter is the output torque produced by a torque-producing member, and wherein said sensing means comprises means for sensing motion of said torque-producing member relative to a predetermined member.

6. The system according to claim 4 wherein said system is a spark-ignition engine, said second parameter is the output torque of said engine, and said first parameter is the spark timing in said engine.

7. The system according to claim 4 wherein said input signal and said first and second control signals are all fluid signals.

8. A system comprising:

control means responsive to application thereto of a first fluid control signal for varying a first system parameter in a first sense, and responsive to application thereto of a second fluid control signal for varying said first parameter;

sensing means for monitoring a variable second system parameter to provide a fluid input signal in response to variations of said second parameter toward a peak value of said second parameter, said second parameter being variable over a range of values including said peak value as a function of said first parameter;

first fluidic means responsive to the absence of said fluid input signal for alternately applying said first and second fluid control signals to said control means; and

second fluidic means responsive to the presence of said fluid input signal for steadily applying either of said first and second fluid control signals to said control means.

9. The system according to claim 8 wherein said system is a spark ignition engine, said first parameter is the spark timing of said engine, and said second parameter is the output torque of said engine.

10. The system according to claim 8 wherein said second parameter is the output torque produced by a torque-producing member, and wherein said sensing means comprises means for sensing motion of said torque-producing member relative to a reference member.

11. The system according to claim 8 wherein said first and second fluidic means include:

fluidic oscillator means for providing a train of fluid pulses; fluidic pulse converter means having a first stable state in which it applies said first fluid control signal to said control means, and a second stable state in which it applies said second fluid control signal to said control means, said converter means being responsive to application ofa fluid pulse thereto for switching between said stable states; and

fluidic gating means responsive to said fluid input signal for inhibiting application of said train of fluid pulses to said pulse converter means and responsive to the absence of said fluid input signal for applying said train of fluid pulses to said pulse converter means.

12. The system according to claim 8 wherein said sensing means additionally provides a second fluid input signal in response to variations of said second parameter away from said peak value, said system further comprising pulse generator means responsive to said second fluid input signal for applying a single pulse to said pulse converter means.

13. In combination:

a torque-producing element;

sensing means for monitoring the torque of said torqueproducing element by sensing motion of said torqueproducing element relative to a reference location;

means responsive to motion sensed by said sensing means for providing a differential pressure of a first polarity for motion of said element in a first direction and ofa second polarity for motion of said element in an opposite direction;

means for providing a train of fluid output pulses in response to said differential pressure having said first polarity; and

means for providing a single fluid output pulse in response to said differential pressured having said second polarity.

14. In a system:

a member;

output means;

sensing means for monitoring motion of said member relative to a reference location and providing a differential pressure with a first polarity when said member moves in a first direction and with a second polarity when said member moves in a second direction;

a fluidic oscillator for continuously generating a train of fluid pulses;

fluidic gating means responsive to said differential pressure having said first polarity for passing said train of fluid pulse to said output means; and

fluidic pulse generator means responsive to said differential pressure having said second polarity for applying a single fluid pulse to said output means.

15. In combination:

input means for selectively providing a differential pressure at one of first and second polarities;

output means;

means responsive to said differential pressure at said first polarity for applying a train of fluid pulses to said output means; and

means responsive to said differential pressure having said second polarity for applying a single pulse to said output means.

16. The system according to claim 15 wherein said output means includes means responsive to fluid pulses applied thereto for controlling the polarity of the differential pressure provided by said input means. 

